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Neuro - Physiology > Sensory Systems > Flashcards

Sensory Systems Flashcards

1
Q

a stronger stimulus will give a greater amplitude or frequency

A

greater frequency

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2
Q

a longer stimulus will give greater length of signal or greater frequency

A

greater length

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3
Q

which primary afferent fibres signal is fastest

A

a-beta -thickest and myelinated

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4
Q

what do a-beta fibres receive

A

touch, pressure, vibration and proprioception

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5
Q

what do a-delta fibres receive

A

cold, fast pain and pressure

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6
Q

what do c fibres receive

A

warmth and slow pain

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7
Q

which of the 3 fibre types is the biggest and most myelinated

A

a-beta (hence fastest signal)

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8
Q

which fibre is unmyelinated

A

c fibres (hence slowest signal)

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9
Q

which two types mediate pressure

A

a-delta and a-beta

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10
Q

which two types mediate proprioception

A

a-alpha and a-beta

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11
Q

what is the dorsal root ganglion equivalent in the head

A

cranial nerve ganglia (nuclei)

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12
Q

the area a nerve is responsive to stimulus over is its _______ field

A

receptive

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13
Q

a nerve will _____ to send a AP

A

depolarise

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14
Q

a deeper receptor is more/less accurate

A

less accurate

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15
Q

what are the 3 types of primary afferent fibres of cutaneous sensation

A

A-beta, A-delta and C

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16
Q

what are the 2 types of primary afferent fibres of proprioceptin

A

A-alpha and A-beta

17
Q

what types of sensory nerves that we know about are A-alpha or A-beta

A

muscle spindles and golgi tendons as in stretch and inverse stretch reflexes

18
Q

afferent fibres of pain

A

A-delta and C fibres

19
Q

how do all primary afferent fibres enter the spinal cord

A

through the dorsal root ganglion (or cranial nerve ganglia in head)

20
Q

how do A-alpha and A-beta fibres travel up the spinal cord

A

they go up the dorsal column, synapse with 2nd order which then cross the midline and project up to the thalamus and so on

21
Q

how do A-delta and C fibres travel up the spinal cord

A

they are thermo and nociceotive so they synapse and cross over at entry and travel in the spinothalamic tract

22
Q

where does all the sensory information terminate

A

somatosensory cortex (postcentral gyrus)

23
Q

what happens when a stimulus is held for a long time

A

they APs stop. they will fire again when the stimulus is removed (like wearing clothes)

24
Q

what pathway feature may explain referred pain

A

convergence

25
Q

convergence increases/reduces acuity

A

reduces

26
Q

when you touch an area of skin what is the effect on the surround nerve endings that are not being touched

A

they receive lateral inhibition

27
Q

benefit of lateral inhibition

A

gives a sharper cleaner sensory image and borders are more defined

28
Q

explain the gate control theory of pain

A

when A-alpha/beta neurons are excited and enter the spinal cord they stimulate inhibitory interneurones that release opioids (endorphins) to act on the A-delta/C neurones

when the original signals reach the midbrain this inhibition is further stimulated

29
Q

effect of prostaglandins on bradykinin and thus on pain

A

prostaglandins sensitise nociceptors to bradykinin.
bradykinin is released in response to noxious stimuli which stimulates nociceptors.
prostaglandins therefore help pain signals be sent

30
Q

when is bradykinin released

A

when there is a noxious stimulus

31
Q

how do NSAIDs work to block pain

A

they inhibit cyclo-oxygenase enzyme (which generates prostaglandins) and so desensitise the nociceptor to bradykinin

32
Q

local anaesthetic block which electrolyte responsible for action potentials

A

Na+ - all axonal transmission is blocked

33
Q

how does TENS work

A

it stimulates mechanoreceptors at same level as pain and so stimulates the inhibitory opioid pathways blocking 1st to 2nd order neuron synapse

34
Q

what class of analgesics activate descending inhibitory pathways

A

opiates e.g. morphine

35
Q

what class of analgesics blocks transmitter release in dorsal horn when given epidurally

A

opiates e.g. morphine

36
Q

which classes of analgesics reduces nociceptor sensitivity

A

opiates and NSAIDs

Neuro - Physiology (16 decks)

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